Characteristics related to body colour of myodocopid ostracods were classified and examined. Two new characteristics were found: a structural colour on spermaducts and a carapace colour change. Many cypridinid species possess a blue colour in spermaducts. This is probably related to a copulation display or mate recognition. The carapace colour change was observed in Codonocera sp.. It was caused by regulating chromatophores. Additionally, pigmentsobserved in digestive organs were classified into three groups: a typical dark-brown pigment and two kinds of colourful pigment. The latter pigments are expressed in two different lineages, respectively. Finally, relationships between the characteristics mentioned above and phylogeny are discussed.原著2014 年度神奈川大学総合理学研究所共同研究助成論文